Glass sealed beam headlamps have been used in motor vehicles for some time and a rectangular shaped headlamp unit has been introduced more recently which includes mounting or seating pads formed in the glass reflector member of said assembly when initially pressed. These mounting pads are solid boss elements located at each corner of the rectangular-shaped reflector member in the sealing rim region to provide means for mounting the reflector after having the glass lens member hermetically sealed thereto in the headlamp receptacle of the vehicle. Problems were encountered when solid mounting pads were molded as part of a unitary construction in a plastic PAR lamp reflector having the same general rectangular shape, however, due to excessive shrinkage of the plastic material upon cooling. More particularly, the amount of plastic in said solid plastic boss elements produced enough shrinkage at the corners of the rectangular shaped member to both deform the parabolic cavity of said member at these locations as well as deform the sealing rim in adjacent regions and thereby hamper obtaining a leak-proof seal when the lens member of the unit is assembled thereto. It would be desirable to avoid all such deformation in a manner which does not require substantial alteration of the existing reflector configuration.